1. Field of the Invention
The present invention relates generally to trowel blades. More particularly, the present invention relates to trowel blades having engagable cleats attached thereto to receive a removable handle for the blade.
2. Related Art
Trowels are used in a variety of construction applications including flooring installation, tile laying, concrete finishing, etc. As trowels are generally subject to repeated contact with abrasive surfaces or materials, the blade of the trowel is often formed from a substantially hardened blade material, such as hardened steel, to prolong a usable life of the trowel blade. Typically, such materials are hardened and tempered by a steelmaker who tensions continuous strips of the material while subjecting the material to various processes, such as heat extremes and/or chemical treatments introduced into a carefully controlled atmosphere surrounding the strips being treated. The hardened and tempered blade material is then often sold in roll form to trowel manufacturers, who then form individual blades from the roll of sheet material. As the hardening and tempering of the blade material is generally done on a large scale, it is not generally feasible to harden and temper the blade material prior to forming individual trowel blades.
During the individual trowel blade manufacturing and assembly process, the trowel manufacturer generally cuts the rolls of strip material provided by the steelmaker into single, substantially rectangular blades. The trowel manufacturer also must generally attach some type of handle to each of the blades, to provide an interface for a user of the trowel. In some applications, engagement cleats are coupled to or with the blade to allow a handle to be removably attached to the blade. As the individual blades have already been hardened and tempered prior to attaching of a handle, this handle attachment process has proved problematic.
For example, many attachment methods require or create the presence of heat. If a handle is welded to the blade, the heat from the welding process can disturb the heat-treated surface of the blade, causing the blade to warp, become too brittle and fracture, and/or to lose its hardness. In addition, during the hardening of the blade material, grain structure is often formed on or beneath the surface of the blade material which provides a finished, “brushed” appearance to the blade material. Maintaining the finished surface can be important to trowel manufacturers, as the finished surface can limit corrosion of the blade and can hide “smudge” marks or fingerprints on the blade. Thus, in addition to compromising the structural integrity of the blade, welding can mar the surface finish of the hardened blade, undoing much of the work performed in the controlled hardening process. Repairing or concealing such damage to the blade can be extremely difficult.
These problems associated with attempting to weld a handle or engagement cleat to the blade are also significant if grinding or other machining processes are performed on the trowel blade when attempting to attach a handle.
For these reasons, attempts have been made to attach handles or cleats using processes that do not require or generate heat. One such attempt involves the use of rivet fasteners which either attach a handle to the blade or attach cleats to the blade for removably receiving a handle. In particular, rivets have been used to attach plastic cleats to a trowel blade, as described in U.S. Pat. No. 5,193,244, which is herein incorporated by reference. In this process, a dimple is generally first formed in the trowel blade. A rivet is then inserted through a bottom of the blade in the dimple and through a plastic cleat protruding above the trowel blade. The rivet is then deformed into a top of the plastic cleat.
While this system has met with some degree of success, it has been found that the trowel blade is often deformed outside of the area of the dimple when forming the initial dimple, causing the blade to have surface irregularities that lead to gaps formed between the removable handle and the blade. The gaps can allow adhesives and other materials to seep between the blade and the handle.
In addition, the system disclosed in U.S. Pat. No. 5,193,244 relies on a lower, pre-formed rivet head that is seated within the dimple below the blade. In the case where the pre-formed rivet head does not precisely match the geometry of the dimple, the cleat can be cocked with respect to the blade, as the pre-formed rivet head may become cocked within the dimple and distort the plastic cleat upon deformation of the rivet in the plastic cleat. In addition the pre-formed rivet head may extend below the lower surface of the trowel blade, possibly interfering with the application in which the trowel is to be used.